DC-HIL-Fc binds to activated (but not resting) T cells. (A) Purified splenic CD4⁺ T cells were cultured with concanavalin A (10 μg/mL) for 3 days. After blocking the binding activity of Fc receptors on cells with a Fc blocker, treated T cells were stained with DC-HIL-Fc/ FITC-anti-human IgG Ab (open histograms), or corresponding control Abs (gray histograms). Binding of DC-HIL-Fc to T cells was analyzed by FACS. (B) Purified CD3⁺ T cells were treated with immobilized anti-CD3 Ab (1 μg/mL) for 3 days and then stained with FITC-labeled anti-CD4 or anti-CD8 Ab and with DC-HIL-Fc or hIgG/PE-anti-human IgG. Numbers in each quadrant represent percentages of the total cell population. Data shown are representative of 3 independent experiments.